1. Field of the Invention
The present invention relates to protocols for use with infra-red (IR) transmitting devices, e.g., the IrDA (Infra-red Data Association) transmission protocols, and, more particularly, to a method and means for providing transition support for IrDA-compatible systems including transceivers with media sense.
2. Prior Art
The Media Access Control (MAC) rules of the IrLAP (Link Access Protocol) specification presently being discussed by the IrDA for standardizing infra-red (IR) communications (this and related standards information are available electronically on the IrDA web site located at xe2x80x9cirda.orgxe2x80x9d) require that before initiating an IR transmission a transceiver device must be set to listen for at least 500 ms and detect no IR data link connection during that time. This 500 ms delay may cause problems with certain systems in which the IrLAP specification might be applied, such as remote controllers. These delay problems can be avoided to some extent if the transmitter device is set to continuously listen in the IR domain. In such case, if no IR traffic is detected when transmission is requested, a connection-less data transmit request can be fulfilled instantaneously, whereas in the usual case connection-less services are slowed down. However, such continuously listening devices have a major drawback when traffic is detected in the IR domain as the device is rendered useless until the IR domain is free and available to transmit.
Alternative approaches that could be used to make the IrDA protocols more attractive for use with remote controllers, include:
the MAC rules could be relaxed in the IrLAP specifications in such a way that the connection-less data service would have relaxed MAC, since connection-oriented data transmission is able to recover from occasional lost frames when prevented from being sent by a connection-less data frame; or
low-end devices could be authorized to emit a connection-less data frame even if they detect other traffic, but some rules concerning timing limits would have to be generated so that the connection-less data would not destroy a link connection; or
the user data for higher layers, i.e., objects, could be placed in the XID frames used for sniffing, which would give access to the relaxed MAC of the sniffing frames.
From a hardware standpoint, systems in the consumer electronics field require longer transmission distances than those supported by most IrDA-SIR (the official IrDA specification) implementations. Thus, consumer electronics applications may require changes in the IrDA-SIR definition for the minimum distance required from transceiver devices and for the maximum output power that may be used.
The IrDA connection-oriented data service specifications do not fit inside the limitations of consumer electronics devices. The size of the implementation and the processing power required rule out the use of the connection-oriented data service as a viable option in this regard. To achieve connectivity between IrDA devices supporting IrDA specifications and devices in the consumer electronics field, a common minimum functionality must be selected in such a way that both high-end desk top systems and low-end systems, such as remote controllers, can rely on this functionality.
Problem to be Solved:
It is therefore a problem in the art to combine the functionality of the connection-less data service of the IrLAP and IrLMP (Link Management Protocol) with object encapsulation rules, as defined in IrDA object exchange (OBEX) specifications, to accomodate various IR transceiver devices particularly those used in consumer electronics.
Object:
It is accordingly an object of the present invention to provide a method and means for providing transaction support for IrDA-compatible systems including transceivers with media sense.
It is another object of the present invention to provide such support by placing the object exchange rules of the IrDA OBEX specifications in the data of the connection-less service of the IrLAP and IrLMP protocols.
The present invention involves a method and means to adapt the MAC rules of the IrLAP specification to accomodate various IR transceiver devices with or without media sense. The invention utilizes an IrDA protocol stack having a series of layers including:
where OSI is Open Systems Interconnection and LSAP is the Link Service Access Point.
This kind of protocol stack can be applied to a very large variety of devices, such as, remote controllers with feedback for tuners, televisions, videos, audio equipment, and PCs. Also, it can be used for data transactions by request, e.g., pager reporting of received numbers, phone reporting of caller ID, or cellular telephone sending of a phone book entry. Further, it is applicable to data acquisition systems, such as, portable GPS reporting of changes of location and medical systems.
Various ways for implementing the invention comprise:
Using the connection-less data service;
Using XID frames; or
Using proprietary or open object definitions.
The preferred approach is to use the connection-less data service that is already present in the IrDA specification along with the emerging OBEX object definitions. This approach requires no changes in existing systems and the open service specification ensures connectivity between systems from different vendors.